Cooperative robotic system for handling a geometrically unknown object

Abstract

The current paper presents a new approach for cooperative control of a robotic system for grasping and handling an object with unknown geometry. The robotic system consists of three Cartesian robots with three degrees of freedom. The unknown object is approximately represented by three two-degrees-of-freedom virtual links of unknown length. Considering each of the virtual links as part of the corresponding robot, three five-degrees-of-freedom robots result that coordinate with each other as a closed kinematic chain. To cope with the kinematic uncertainty of the object, an adaptive algorithm consisting of a kinematic adaptation law is developed herein.

For designing the controller, the dynamic equations of motion are transformed from joint space to the object space. In other words, the system dynamic is decoupled into a locked system and a shaped system. A proportional–derivative controller and a proportional–integral–derivative controller are developed for the shaped and locked systems, respectively.

The object is modelled in the SimMechanics toolbox of MATLAB, and the controllers are simulated in the Simulink environment. Simulation results show that the proposed kinematic adaptation law together with the control system gives good performance for the cooperative system.